The present invention relates to an apparatus having a plurality of self-adjusting support and biasing members for supporting and prealigning polygonal and other cross-sectional shaped bars such as hex or square stock bar sections or stock having different diameters before chucking in the collet of machine tools so that the operation performed on the work piece can be efficiently carried out.
Many automatic and manual machine tools are of the type in which the feed material is a metal bar, or bar stock, of a length considerably greater than the parts to be produced from it, wherein the stock is typically in 12 to 16 foot sections. Since the manufacturing operation takes place at one end of the bar stock while it is rotating clamped in a chuck mechanism, it is necessary that the entire length of stock rotate. Generally, the stock is fed to the chuck through a cylindrical spindle in the headstock of the machine tool at rates of about 1,200 to 1,500 feet per hour, wherein the inside diameter of the spindle is sized to closely fit the outside diameter of the largest bar stock to be used, typically about 3/4 of an inch in diameter. However, the diameter can vary greatly and it is not practical to change headstocks when bar stock of other diameters or polygonal shaped bar stock is used.
When smaller bar stock is held in the chuck mechanism and rotated, the bar stock within the spindle tends to move out of concentric rotation and the resulting movement can cause poor surface finish on the machined parts and problems associated with the control of the machining operation. Commercially available control guides fail to correct the problem caused by nonuniformity in the size or cross-sectional shape of the bar stock.
Most machine tool operations also include a bar feeding and/or support device such as an automatic bar-loader for holding one or more bars within a tubular trough or guide and utilizing a bar pushing device to push and guide the bar stock in position so that the inlet end of the headstock is in position for insertion in the collet of the chuck. In order to allow insertion of the shaped bar within the chuck, the profile of the bar and that of the collet must coincide during insertion. Even if the chuck is rotating, the bar in fact fails to enter the collet, since it is forcefully pushed against the noncomplementary surface and it too is rotated, preserving an angular offset. On the other hand, even if the bar is not rotated, the moment during which it is in step with the collet is very short, and insertion is impossible since the advancement system has considerable inertia.
Accordingly, it is a principal object of the present invention to provide a self-adjusting bar stock support to minimize undesirable radial or lateral motion of the bar stock.
It is another object of the present invention to provide a self-adjusting bar stock support which can accommodate different diameters and bar stock of different transverse cross-sectional shapes, and bar stock having nonuniformities, all with one size support.
It is another object of the present invention to provide a self-adjusting bar stock support which is economical and of simple manufacture.
It is therefore another object of the present invention to solve the above described problem by providing a prealignment device capable of aligning the bar stock with the collet of a chuck.
It is an object of the present invention to provide an adjustable means responsive to angular displacement of the bar stock to restore the normal longitudinal position of the tool for proper alignment within the collect.
Another object is to provide a means of prealignment of bar stock which is easily installed in a working position and easily disconnected therefrom, convenient in use, economical of manufacture, simple to construct, and easy to service.